The present invention relates to a module for optical communication where optical elements for transmission and for reception are used in directional communications, or to a module for optical communication provided with optical receiving elements for monitor use.
A module for directional communication shown in FIG. 5 is arranged in the body 7 so that the optical element 1 for transmission use and the optical element 2 for reception can become orthogonal in their mutual optical axes. A beam splitter plate 3, as an allotment body for light signals in the crossing portion of the mutual optical axes, is included at 45.degree. with respect to the mutual optical axes. A ferrule 6 having retained an optical fiber 5 is arranged in the optical axis direction of the optical element 1 for transmission.
The transmission light 20 outputted from the optical element 1 for transmission use passes through a lens 4, and is partially reflected by a beam splitter plate 3 to transmit the remaining portion of it. The transmitted transmission light 20 is guided out by the optical fiber 5. The received light 21 introduced from the optical fiber 5 is partially transmitted by the beam splitter plate 3 and is reflected in its remaining portion. The received light 21 reflected becomes incident into the optical element 2 for reception, thus making it possible to communicate in both directions.
The beam splitter plate 3, a glass plate, partially reflects the light signal and conducts a distribution operation through transmission of the remaining portion. As a distribution body of light signals, a prism type splitter or a hologram is used.
However, the module for bi-directional communication shown in FIG. 5 has a problem in that the component, reflected by the beam splitter 3, of the transmission light 20 outputted from the optical element 1 for transmission includes further stray light 22 transmitting through the beam splitter 3 by reflection by the inner wall face 7c of the body 7, and the stray light 22 becomes incident into the optical element 2 for reception to make the crosstalk characteristics worse.